/*
 * Copyright (c) 2011-2012 Alexander Dubu
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * o  Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * o  Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * o  Neither the name Axil nor the names of its contributors may be used to
 *    endorse or promote products derived from this software without specific
 *    prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package axil.api.extend;

import java.io.Reader;


/**
 * An interface defined for loading the source form of modules, functions and
 * operators. By default, Axil has an adapter pre-installed that can load the
 * Axil standard library. Host applications that define their own types and
 * functions will need to provide their own adapter. This interface is intended
 * to be implemented by host applications, as necessary.
 *
 * @see axil.api.Axil#install(SourceAdapter)
 */
public interface SourceAdapter {
	/**
	 * The type of definition file.
	 */
	public enum Kind {
		/**
		 * A type definition, where the type is defined as XML.
		 */
		TYPE,

		/**
		 * A type definition, where the type metadata is defined as XML.
		 */
		FUNCTION,

		/**
		 * An operator definition, where the operator metadata is defined
		 * as XML.
		 */
		OPERATOR
	}


	/**
	 * Provide a string reference for the given reader. The reference is
	 * intended as a diagnostic aid when problems are encountered.
	 *
	 * @param reader
	 * 	A Reader object as returned from either the module() or definition()
	 * 	methods of this class. The reader given cannot be null.
	 *
	 * @return
	 * 	Returns a reference sufficiently complete as to be unambiguous as to
	 * 	the source. For example, if the source is a file, it would be the
	 * 	absolute path to the file, not just the filename.
	 */
	public String reference(Reader reader);


	/**
	 * Return a reader object for a module definition.
	 *
	 * @param ident
	 * 	The name of the module. The identifier given is never null or empty.
	 *
	 * @return
	 * 	Returns an open and ready-to-use reader object. A null value is returned
	 * 	if this adapter cannot find the module definition.
	 */
	public Reader module(String ident);


	/**
	 * Return a reader object for a definition of the given kind of object.
	 *
	 * @param module
	 * 	The module in which the named function resides. The module given is
	 * 	never null or empty.
	 *
	 * @param kind
	 * 	The type of definition desired.
	 *
	 * @param ident
	 * 	The name of the object, such as the function or operator name. This is
	 * 	the name, without any decoration. For example, "abs", not "abs()". The
	 * 	identifier given is never null or empty.
	 *
	 * @return
	 * 	Returns an open and ready-to-use reader object. A null value is returned
	 * 	if this adapter cannot find the definition.
	 */
	public Reader definition(String module, Kind kind, String ident);
}
